1992 BMW 525i M50 engine idle problem

[bissellh]

Thanks! I will search the frum on the O2 sensor. I did the stomp test. I have not fault codes and no check engine light or other related dash indicators. I do not think it could be the O2 sensor because it, like the AFM, runs hot anyway. I will not rule it out as a possibility though and will search the forum on it. Thanks again!

[bmwrp8]

Thanks! I will search the frum on the O2 sensor. I did the stomp test. I have not fault codes and no check engine light or other related dash indicators. I do not think it could be the O2 sensor because it, like the AFM, runs hot anyway. I will not rule it out as a possibility though and will search the forum on it. Thanks again!

just try or check your engine bay wirings mine was like that before but its the other way around it has issues when its cold but its fine when warmed up turns up to be my ICV. keep me posted i'm curious also

[bissellh]

I cooled the camshaft sender and the crankshaft sensor with carb cleaner to see if that would help the idle problem. It did not seem to help.

I wonder what control/sensor could be affected most easily by outside temperatures.

I also observed that just idling the car in the cold temperatures without opening the hood, helped the idle problem. I previously stated that opening the hood to cool the engine compartment helped the idle problem. Now, I wonder. Perhaps, it was coincidence and the problem is not related to engine compartment temperature at all. Or perhaps it is, and the engine compartment temperature cools down much sooner at idle with the hood closed in colder temperatures.

If engine compartment temperature is unrelated, perhaps it is the oxygen sensor. It is the emission component most exposed to outside air temperatures.

[Morgenster]

I cooled the camshaft sender and the crankshaft sensor with carb cleaner to see if that would help the idle problem. It did not seem to help.

I wonder what control/sensor could be affected most easily by outside temperatures.

I also observed that just idling the car in the cold temperatures without opening the hood, helped the idle problem. I previously stated that opening the hood to cool the engine compartment helped the idle problem. Now, I wonder. Perhaps, it was coincidence and the problem is not related to engine compartment temperature at all. Or perhaps it is, and the engine compartment temperature cools down much sooner at idle with the hood closed in colder temperatures.

If engine compartment temperature is unrelated, perhaps it is the oxygen sensor. It is the emission component most exposed to outside air temperatures.

If you want to reach the ICV it's pretty doable without removing the manifold or going all bendy under the car. You just remove the oil filter cap from the housing to enlarge the space for your left arm. You disconnect the elbow hose from ICV to manifold and take it out first and then disconnect ICV electrical plug en push out ICV through rubber ring. The ICV intake hose is better left on the ICV because it's a bitch to get back on and nearly impossible while under the manifold. I did it and had some trouble getting it back in place but I made it. The procedure can be found somewhere on the net but I can't remember the link. Google will help.
I doubt your ICV is the problem though.

[Ferret]

Idle bounce + No fault codes = usually manifold air leak.

When I bought my first 525i, it used to do this after a rebuild - the usual suspect is the hose that runs to the ICV.



Have a look in the general location of 12 and look for cracks in any part of 10 - that's what was causing idle hunting in mine.

Also watch out for cracking in 3 around where the grommets enter the rubberwork - cracks here can cause problems too.

[bissellh]

Was your hunting idle happening only after the engine warmed up or was it all the time???

[Ferret]

Was your hunting idle happening only after the engine warmed up or was it all the time???

It was only happening after warm up, it'd run happy as larry while cold.

Once warmed up though it was an absoloute bitch, the bouncing combined with the auto box made for fun at a stop light.

I think it's either something to do with ignoring the MAF output during warm up, or something to do with the warmth of the rubber hoses - they become more supple when warmed up and let air leak more. Bullsh*t guess at the temp reason though.

All the air hose rubberwork was shot to crap on my '92 - I'd give yours a thourough inspection, and check for hairline cracks in the rubberwork.

[bissellh]

That sounds like exactly the same problem I am having!

I actually just replaced my engine after my old one overheated while my girlfriend was driving to work. She just kept going until the engine blew up. Needless to say she will not be driving it anymore. My 'new' engine only has 80K compared to the 230K on my car and it pulls very nicely.

I have already fixed some vaccum leaks around the throttle body and AFM. I bet I have some around the ICV too. I have already purchased some fuel line hoses to replace vacuum hoses and some new intake and throttle body gaskets. I bet that if I pull the intake off and replace all hoses and check all fitments it would resolve the problem.

[BillionPa]

... air intake temp sensor test time?

if you dont remember installing a new O2 sensor in the last 70000 miles, replace it now!

[Ferret]

That sounds like exactly the same problem I am having!

I actually just replaced my engine after my old one overheated while my girlfriend was driving to work. She just kept going until the engine blew up. Needless to say she will not be driving it anymore. My 'new' engine only has 80K compared to the 230K on my car and it pulls very nicely.

I have already fixed some vaccum leaks around the throttle body and AFM. I bet I have some around the ICV too. I have already purchased some fuel line hoses to replace vacuum hoses and some new intake and throttle body gaskets. I bet that if I pull the intake off and replace all hoses and check all fitments it would resolve the problem.

With the engine running and the idle bouncing, pull the plug on your MAF and see if it suddenly starts running stable again.